fix some warts in IO

- remove TcpPipelineHandler’s type parameter
- remove not-accept() failure test (which is completely bogus)
- add comments explaining more about TcpPipelineHandler.Init
- remove the funny “manager” from the Server example
 #3378 - fixing memory leak in LARS.stop
add BackpressureBuffer, see #3253

- also make a Write’s “ack” be a Tcp.Event (to suit pipelines)
- add stress test for BackpressureBuffer
- add it to SslTlsSupportSpec
- add it to the docs
add ScalaDocs and correct UDP docs, see 3268
split IO docs and mark them EXPERIMENTAL, see #3294
fix one more warning
Change default tick-duration to 10ms, see #3387
Include path in error message for missing router conf, see #3178
Merge pull request #1477 from akka/wip-3387-scheduler-resolution-patriknw

Change default tick-duration to 10ms, see #3387
Merge pull request #1482 from akka/wip-3378-fix-memory-leak-in-lars-stop-√

 #3378 - fixing memory leak in LARS.stop
Merge pull request #1475 from akka/wip-3178-err-msg-router-patriknw

Include path in error message for missing router conf, see #3178
a few fixes after review of the IO doc changes
Merge pull request #1483 from akka/wip-IO-docs-∂π

several things IO
Merge branch 'master' into wip-2996-make-things-compile-and-test-on-ppc-j9-ban

Conflicts:
	akka-cluster/src/multi-jvm/scala/akka/cluster/StressSpec.scala